Non-aqueous electrolyte secondary battery and method for producing non-aqueous electrolyte secondary battery

Abstract

Provided is a technique for suppressing the formation of black regions in a wound electrode body. The production method disclosed herein is a method for producing a non-aqueous electrolyte secondary battery that includes a wound electrode body, a non-aqueous electrolyte, and a battery case. This production method includes the following steps: an assembling step S 1 of placing the wound electrode body and the non-aqueous electrolyte in the battery case to construct a secondary battery assembly; a first step S 2 of performing initial charging on the secondary battery assembly; and a second step S 3 of setting the temperature of the wound electrode body to 50° C. or lower and keeping this state for at least 72 hours after the first step.

What is claimed is: 
     
       1. A method for producing a non-aqueous electrolyte secondary battery that comprises
 a flat-shaped wound electrode body in which a belt-shaped positive electrode plate and a belt-shaped negative electrode plate are wound, with a belt-shaped separator being intervened therebetween; 
 a non-aqueous electrolyte; and 
 a battery case that houses the wound electrode body and the non-aqueous electrolyte, 
 the negative electrode plate comprising a negative electrode core and a negative electrode active material layer formed on the negative electrode core, and 
 the negative electrode active material layer having a length of at least 20 cm in a winding axis direction of the wound electrode body, 
 the method comprising: 
 an assembling step of placing the wound electrode body and the non-aqueous electrolyte in the battery case to construct a secondary battery assembly; 
 a first step of performing initial charging on the secondary battery assembly, wherein the secondary battery assembly is charged so that the state of charge (SOC) of the secondary battery assembly is 50% or less; and 
 a second step, wherein the secondary battery assembly after the first step is maintained in a state with a SOC of 50% or less and a temperature of 50° C. or lower and this state is maintained for at least 72 hours. 
 
     
     
       2. The production method according to  claim 1 , wherein
 the secondary battery assembly is restrained in a thickness direction of the wound electrode body in the second step. 
 
     
     
       3. The production method according to  claim 1 , wherein
 the battery case comprises an exterior body that comprises an opening and a bottom part opposite to the opening, and a sealing plate that seals the opening, and 
 the wound electrode body is arranged in the exterior body, wherein the winding axis is parallel to the bottom part. 
 
     
     
       4. The production method according to  claim 1 , wherein in the first step the secondary battery assembly is charged so that the SOC is 5% or larger and 30% or less. 
     
     
       5. The production method according to  claim 1 , wherein the first step is performed in a state where the battery case is opened. 
     
     
       6. The production method according to  claim 1 , wherein the second step is performed in a state where the battery case is opened. 
     
     
       7. The production method according to  claim 1 , wherein the battery case is sealed after the second step. 
     
     
       8. The production method according to  claim 1 , wherein the SOC of the secondary battery assembly is 25% or less in the second step. 
     
     
       9. The production method according to  claim 1 , further including:
 a third step of performing charging on the secondary battery assembly after the second step, wherein in the third step, the secondary battery assembly is charged so that the SOC is 50% or lower; and 
 a fourth step of performing aging at 50° C. or higher and 80° C. or lower on the secondary battery assembly after the third step. 
 
     
     
       10. The production method according to  claim 9 , wherein in the third step, the secondary battery assembly is charged so that the SOC is 40% or less. 
     
     
       11. The production method according to  claim 9 , wherein:
 the second step is performed in a condition where the secondary battery assembly is restrained, and 
 the restraining of the secondary battery assembly is released before the third step.